AND RIO GRANDE DO NORTE. BRAZIL. 7 



ments derived from this original laiul mass. It is necessary also, to 

 know that these rocks are not homogeneous hut that they arc hard 

 here and soft and decomposed a few feet away; that they have 

 been crushed, metamorphosed and recrystallized to a remarkable 

 extent, and that one may find a hard granite " serrote " standing 

 out in the midst of an area of soft schist. Everywhere the rocks 

 are cut by quartz veins which range from a few centimeters to 

 half a meter in diameter and occasionally there are pegmatite veins. 

 Mr. Roderic Crandall in his paper entitled " Geographia 

 Geologia, Supprimento d'Agua, Transportes e Agudagem " makes a 

 further division which he calls the " Series Ceara." I have not 

 made this distinction, but have included the rocks of the Ceara 

 series under the more general head of the schists of the Brazilian 

 complex. However, they have a few distinguishing characteristics 

 which I shall give briefly. The Ceara series, where it is distinguish- 

 able, seems to be composed of acid rocks, usually of a light color. 

 They contain more or less kaolin and clay and in some cases have a 

 peculiar earthly appearance. On weathering ofl: they do not weather 

 into rounded boulders with smooth surfaces, but outcrop in jagged 

 exposures and the boulders, large and small, have sharp edges — not 

 rounded ones. The Ceara series usually presents a schistose ap- 

 pearance and in places according to Mr. Crandall, may contain 

 lenses of hard, vitrified sandstone. In other places there are masses 

 of limestone completely isolated in areas of schist. However, there 

 does not seem to be any systematic separation of this series from 

 the other rocks and it is often, if not usually, impossible to make 

 any distinction at all. No attempt has been made by anyone to map 

 them separately. Hence, although all of the schists are i)robably 

 not strictly crystalline, I have included them with the crystalline 

 rocks of the Brazilian com])lex. 



In regard to the distribution of the granites, I have already said 

 that they form the axes of some of the principal serras. Also, they 

 are especially noticeable along the contact of the crystalline mass 

 with the sediments. In such a vicinity the former usually takes the 

 shape of rounded boulders and bosses of granite and gneiss. Small 

 patches of granites, however, are found occasionally outcro])ping 



